Put all you can on the ailerons. That plane is very prone to aileron flutter.

5645s are perfect, run on 6V. Use them all around.

If you want to go cheap you can use 645MG, but if you do, better use carbon rods and ball links and not that stock garbage H9 gives you.

I have seen 3 of these planes go down due to cheap servos and aileron flutter.

DP